/*
 * Copyright (c) 2009, Hamish Morgan. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of the University of Sussex nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
package locusts.server.behaviours;

import java.util.ArrayList;
import java.util.List;
import javax.vecmath.Vector2d;
import locusts.common.entities.Actor;

/**
 * A collection of behaviours that will return the largest magnitude of
 * steering of it's sub components. If more than one sub behaviours is
 * maximum then it will randomly select one of them.
 *
 * @author Hamish Morgan
 */
public class Max extends AbstractBehaviourList {

    public Max(double weight) {
        super(weight);
    }

    @Override
    public Vector2d getSteering(Actor boid) {
        final Vector2d[] forces = getForces(boid);
        final Vector2d steering = max(forces);
        steering.scale((double) getWeight());
        return steering;
    }

    private final Vector2d max(final Vector2d[] vecs) {
        if (vecs == null || vecs.length == 0)
            throw new IllegalArgumentException();
        if(vecs.length == 1)
            return vecs[0];
        
        List<Vector2d> argmaxs = new ArrayList<Vector2d>();
        argmaxs.add(vecs[0]);
        double maxLen = vecs[0].lengthSquared();

        for (int i = 1; i < vecs.length; i++) {
            final double len = vecs[i].lengthSquared();
            if (len >= maxLen) {
                if (len != maxLen) {
                    maxLen = len;
                    argmaxs.clear();
                }
                argmaxs.add(vecs[i]);
            }
        }
        return argmaxs.get((int)(Math.random() * argmaxs.size()));
    }
}
